Wikipedia:Reference desk/Archives/Science/2016 December 29

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December 29

Commercially-canned mushrooms

There's something different about commercially-canned button mushrooms, compared to fresh ones. Fresh mushrooms are soft. When you break them, they break along the grain of the fibers. Canned mushrooms, on the other hand, are firm, and have a seemingly "isotropically uniform" texture. What kind of processing and/or added ingredients are responsible for the firmness and texture of canned mushrooms? --100.34.204.4 (talk) 02:32, 29 December 2016 (UTC)

Maybe because they're canned in brine, which partially dries them out? 2601:646:8E01:7E0B:E5C0:72CB:AF6F:FD32 (talk) 03:34, 29 December 2016 (UTC)

Cooking does it. If you cook fresh button mushrooms, they will develop a similar texture. In fact the longer you cook them the tougher they get. Looie496 (talk) 05:03, 29 December 2016 (UTC)

Is that it? How long do you have to cook button mushrooms to give them the texture of canned mushrooms? The cooked fresh mushrooms I've seen, whether served in restaurants or prepared at home, never seem to have the same firmness and texture as mushrooms that come in a can. --100.34.204.4 (talk) 06:22, 29 December 2016 (UTC)

I have to admit, I'm with the IP in being unconvinced it is simply cooking since I don't think I've ever had button mushrooms with a similar texture or taste to that of canned although I guess I've never cooked them in brine. Nil Einne (talk) 11:25, 29 December 2016 (UTC)

This source [1] does however suggest the general preparation just involves blanching in steam or liquid water then pressure cooking the cans. Nil Einne (talk) 11:31, 29 December 2016 (UTC)

I still think it's mainly a matter of cooking. People who cook mushrooms at home generally don't want that "canned mushroom" texture and cook in a way that avoids it -- that means sauteing the mushrooms until they just begin to deliquese, and then stopping. If you stop at the right point you get a mushroom that is chewy but not rubbery. If you continue to cook the mushrooms after that, the longer you go the more rubbery they get. Looie496 (talk) 14:12, 29 December 2016 (UTC)

Long-term effects of high electric current on copper wire

Are there any long-term effects of high electric current on the physical/chemical properties of copper wire?--My Chemistry romantic (talk) 10:31, 29 December 2016 (UTC)

If it's strong enough to cause ohmic heating, then the heat could cause recrystallization, annealing and surface oxidation (or, if high enough, outright melting) -- but in the absence of ohmic heating, no. 2601:646:8E01:7E0B:E5C0:72CB:AF6F:FD32 (talk) 11:01, 29 December 2016 (UTC)

I had an idea that literature on the lifespan of high tension power lines would hold the answer, but they all seem to agree (like this one) that the ultimate cause of failure of virtually all power line failure can be traced back to environmental issues or manufacturing defects. Heat and electrical arcing can cause a power line to destroy itself, but only after damage has occurred from some other cause. This doesn't directly answer your question, but does suggest that any such effects are minor or non-existent in a well-made wire, if used only as directed. Someguy1221 (talk) 11:04, 29 December 2016 (UTC)

See Electromigration.--Phil Holmes (talk) 15:09, 29 December 2016 (UTC)

Only if the current is DC. 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 02:27, 30 December 2016 (UTC)

Plain copper wire is used for some distribution lines but not so much for high voltage transmission lines. For either type of line, prolonged high current, especially under adverse conditions (full sun, low wind) the conductor heats up and can sag due to expansion, sometimes until it touches trees beneath the conductor and causes an outage. When one line fails this way, the remaining lines can become more heavily loaded and a widespread blackout can ensue. The sources I found online do not, however suggest that the sag is permanent, and imply the sag returns to the normal amount when the line cools off.Edison (talk) 03:19, 31 December 2016 (UTC)

Global warming: have I got this right?

I want to know whether or not I have got this right.

If I have got this right, then according to scientists (as opposed to politicians or non-scientist, corporate spokespeople):

1. Global warming exists and is in progress at this very moment. This is true beyond a shadow of a doubt, or at least as far beyond a shadow of a doubt as, say, the germ theory of disease. (In other words, I might as well try to roll the first ten thousand digits of pi, or decide that this is all a bad dream, as to deny the reality of global warming.)
2. Global warming is largely anthropogenic (i.e. caused by us collectively being just smart enough to be dangerous to ourselves). This is not true beyond a shadow of a doubt; however it is true beyond any reasonable doubt (e.g. I am sure beyond a reasonable doubt that I will not, in fact, marry a princess).

Do I have this right?

Sorry for the tone. I've been off my meds for way too long. 32.212.48.121 (talk) 15:59, 29 December 2016 (UTC)

Just look at the curves [2]. Global warming is exponential now. Any doubt is not based in reality. It is catastrophic. --AboutFace 22 (talk) 16:11, 29 December 2016 (UTC)

OK, so that answers the first half (the is-it-real half) of my question. What about the second half (the is-it-our-fault half)? 32.212.48.121 (talk) 19:44, 29 December 2016 (UTC)

Also look at Global warming, Scientific opinion on climate change and Climate change denial. Alansplodge (talk) 17:33, 29 December 2016 (UTC)

I just saw the slickest piece of anti-warming agitprop I've ever seen here. Now yeah, I realize that's not peer reviewed and it has uncommon odds of being fake. But has anyone actually dug into it well enough to debunk it? You could do a public service here... Wnt (talk) 17:53, 29 December 2016 (UTC)

I didn't look that well mostly because I'm sure there are people who will reply who know far more about it than me, but AFAICT, there aren't really any new claims in that linked blog. Most of it is just repeating classic climate change denial tropes, e.g. on data adjustment that have been dealt with before. There is no need to debunk every single nonsense blog posting when it's just saying the same stuff that has been debunked many many times before. E.g. [3] [4] Nil Einne (talk) 18:07, 29 December 2016 (UTC)

The main adjustment is due to the time of day issue. That's real. The whole problem with all of these things is that we don't have much accurate data, historically speaking, and are comparing straight lines with straight lines+error bars. As soon as someone starts talking about proxies, raise an eyebrow. Greglocock (talk) 21:40, 29 December 2016 (UTC)

Also it confuses US temperature records with the global warming issue. Or at least makes no attempt to disambiguate the two. Greglocock (talk) 21:45, 29 December 2016 (UTC)

1 depends on your timescale. The globe is hotter since 1880 and the Little Ice Age, maybe a little cooler than it was in the Holocene Optimum, and obviously a lot warmer than it was in the last real ice age.

2 If you go through the litany of the new religion, then it goes like this- burning fossil fuels releases CO2 which stays in the atmosphere for a long time. You can check this by looking at how much fossil fuels have been burned, and how much the CO2 in the atmosphere has increased. Adding CO2 to the Earth's atmosphere should increase its greenhouse effect, and hence the Earth's average temperature. You can measure this effect in a laboratory. However the effect is not very large. In order to make CO2 the scapegoat in the computer models the effect is scaled up to match the actual curves of CO2 and temperature since say 1880. The scaling up is justified by calling it positive feedbacks. This is not physics, it is just bad statistics. Cue wiki hivemind... Greglocock (talk) 21:11, 29 December 2016 (UTC)

It should give you some pause that Svante Arrhenius has identified and reasonably quantified the major feedbacks about 50 years before "computer" changed from being a job description to being a machine. These feedbacks are not "scaled up", they are derived from first principles. Yes, there is some matching of parameters to observations, but that is how science works - if you have Newton's theory of gravity, you find the value of the gravitational constant in fundamentally the same way. --Stephan Schulz (talk) 21:50, 29 December 2016 (UTC)

No, you are arguing that the measured value of G in the lab should be arbitrarily scaled to fit G in observations made in the universe. That is NOT acceptable. The correct response is to say wow, we measure G in the lab, and G' in the universe, what is the cause of G-G'? That is science. Saying , oh for the time being we think we'll just use G*x (where x is about 1.5 or more in the case of climate sensitivity) is just silly curve fitting games. Greglocock (talk) 22:47, 29 December 2016 (UTC)

If you measure G' when you are expecting G, then yes of course there is an issue to explain. Scientists have been doing that for decades. Often the explanations are complicated, as natural systems are rarely very simple. Our greenhouse effect is a mixture of absorption by water vapor, carbon dioxide, methane, nitrous oxides, and other gases. Some of these vary by location and/or altitude and the total effect also depends on the temperature and pressure structure as a function of altitude. In addition, transient climate change depends on the heat capacity of the Earth's oceans and land, and the mixing characteristics of the oceans. We can explain all of this if you really wanted to learn the details, but it would take a long time. We already know how to do most of the calculations from first principles to accurately match real world observations. However, this is really just a straw man. You are saying "look at the difference between G and G'", but that's mostly a distraction. Either way, G or G', what you should be paying attention to is that both the simplified theory and the observations imply significant global warming. It is like discovering that your house is on fire and being worried about why your table is on fire but your couch isn't. Dragons flight (talk) 05:36, 30 December 2016 (UTC)

At List of scientists opposing the mainstream scientific assessment of global warming we list "scientists have said that it is not possible to project global climate accurately enough to justify the ranges projected for temperature and sea-level rise over the next century. They may not conclude specifically that the current IPCC projections are either too high or too low, but that the projections are likely to be inaccurate due to inadequacies of current global climate modeling." Just out of curiosity, does anyone reading this believe the opposite -- that they know for sure that current global climate computer models are accurate? If so, how do you know this? Related question: how accurate have previous models been? See [ http://www.drroyspencer.com/2014/02/95-of-climate-models-agree-the-observations-must-be-wrong/ ]. I personally fully agree with the mainstream scientific assessment of global warming, but I simply cannot bring myself to believe in the infallibility of complex computer models written by programmers who's previous models failed to provide an accurate prediction. The scary part is that this leads me to the conclusion that we don't know that the climate won't warm much faster than predicted any more that we know that the climate won't cool instead of warming.

Also see:

• [5] (Key quote: "This rate of warming is significantly slower than that simulated by the climate models")
• [6] (Key quote: "if the past is a guide to the future then uncertainties in climate change are unlikely to decrease quickly")
• [7] (Key quote: "There is this mismatch between what the climate models are producing and what the observations are showing. We can’t ignore it.")
• [8](Key quote: "Reality has deviated from our expectations – it is perfectly normal (& indeed essential) to try and understand this difference.")
• [9] (Key quote: "It's 20 years now, and the average rate of increase in reality is below the lowest trend in the range predicted by the IPCC.")

--Guy Macon (talk) 22:16, 29 December 2016 (UTC)

Incidentally we can take a punt at how much of global warming since 1880 is anthropogenic. Lab climate sensitivity is say 1 deg C per doubling of CO2 (that is a surprisingly flaky number). Since 1880 the concentration of CO2 has increased by about 1/3 of a doubling. So we'd expect 0.3 deg C directly from that. The actual increase has been say 0.8 deg C, so roughly 40% of the rise is directly due to the CO2 from burning fossil fuels. The other 60% is due to things like noise, errors, unconsidered factors, land change use, cloud cover changes, water vapor, other greenhouse gases, the sun, Earth's magnetic field and of course positive (and negative) feedbacks. There are also long term cycles in ocean currents which actually dominate the short amount of good data we have, with a period of roughly 60-70 years and an amplitude peak to peak of 1/2 a degree or so. I don't think 40% can be described as 'largely', I'd be happy to go with 'significantly'.Greglocock (talk) 22:47, 29 December 2016 (UTC)

You're mathetizing wrong. Double is 1 degree. Two doublings is another degree. Three doublings is a third degree. That's geometrical. Arithmetical "doubling" does not exist (2,4,6,8,10). 280ppm*2**0.52 is hey, what do you know, about where we are right now. So there has been 0.52 doublings, 0.52°C. And warmer air can hold more water vapor. This is Meteorology 101. Water vapor is a greenhouse gas (and causes 97% of the greenhouse effect I believe). Sagittarian Milky Way (talk) 00:03, 30 December 2016 (UTC)

Yup, 0.5 doublings, sneaky old logs got me. So, hmm, that leaves me at 0.5 deg C due to CO2 and 0.3 everything else. Fairy snuff. Greglocock (talk) 04:27, 30 December 2016 (UTC)

The figure of 97% (sometimes 95%, sometimes 98%) often is bandied about in the contrarian blogosphere but is incorrect. As our article shows, the correct figure is 36-70%. Shock Brigade Harvester Boris (talk) 01:28, 30 December 2016 (UTC)

Ah, the ratio of water vapor to CO2 in sea level air is not that far from 97:3 and both are 3 atoms in a line molecules so I assumed it was right (I'd already heard two atom molecules like N2 cannot trap infrared) Turns out it was more denialist bullshit. I think I didn't account for water vapor % rapidly decreasing with altitude unlike most gases. Sagittarian Milky Way (talk) 04:57, 30 December 2016 (UTC)

Also see Climate_sensitivity#Equilibrium_and_transient_climate_sensitivity. We are not at equilibrium at the moment, so observed changes underestimate final climate sensitivity. --Stephan Schulz (talk) 02:42, 30 December 2016 (UTC)

• It could very well be that the CO2 has a far greater effect than the computer models predict but there is a huge unknown cooling effect that wipes out 99% of it. Or it could be the other way around. The current scientific consensus is a plausible theory and I accept it because I have not seen any theory that is better (or even close), but "true beyond a shadow of a doubt"? No. That's not science. That's religion. Science gives us "we accept this because it is very, very likely, but we doubt everything and try really hard to disprove it". Climate change theory seems quite solid. On the other hand, the theory that the computer models are accurate and reliable predictors of future climate isn't just a religion. It's a religion that believes that 75 million years ago Xenu brought billions of Thetans to Earth DC-8s, stuffed them into volcanoes, and killed them with hydrogen bombs. --Guy Macon (talk) 04:17, 30 December 2016 (UTC)

• Or it could also be that CO2 has a far smaller effect than the models predict, and other gases have a much bigger impact (such as methane, NOx, or glyoxal). 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 05:22, 30 December 2016 (UTC)

• Exactly right. On the one hand, when it comes to the past, scientists can make educated guesses about such things using the kind of "model" that looks like an equation on a whiteboard. That's bog-standard science, and we should not use the fact that glyoxal might have a huge effect to reject the mainstream view until a scientist or two comes up with a theory where glyoxal does have a huge effect. On the other hand, any theory based solely on the sort of "model" that consists of hundreds of thousands of lines of code and requires a supercomputer to run is likely to be be total bullshit. --Guy Macon (talk) 07:20, 30 December 2016 (UTC)

• The basic science is pretty straightforward, there's a number of things which make it difficult to be very accurate about the rate though. However overall they have a greater accuracy than a doctor who takes a biopsy and says you have a tumor and will probably be dead within two years without an operation. Lots of people will simply blank their mind to such a thing and you get people not going along to the doctor with a lump until it is too late. And yes sometimes such a diagnosis can be wrong. But it is not sensible to depend on that. There is a cost to coping with climate change just like there is a cost to having an operation. Luckily there are not industries which depend on you ignoring cancer. Well actually there is with tobacco. That is what is happening about climate change. Dmcq (talk) 09:03, 30 December 2016 (UTC)

Pure science may be a wrong aproach in this debate because its all focused on statistical data and resulting predictions, which is always very easily disputable because anyone can simply claim that the calculation is wrong or they read to much into the numbers. What no one can dispute is already done damage like the rapidly dying glaciers everywhere in the world. Some of that ice, like the Greenland ice core project proved, is more than 100,000 years old and that will all be gone in 50-100 years. Try claiming the glaciers wont die while everyone can see how they melt away a bit more every year strangely exactly since we started exessively use fossil fuels. No need for numbers or science, just look at any glacier you like anywhere on our planet. What to claim against that? The chineese are secretly stealing all the ice when noone looks? --Kharon (talk) 13:36, 30 December 2016 (UTC)

Its all focused on statistical data and resulting predictions is a common misconception. Modern climate models are not statistical. We have an OK-ish article on general circulation model.

A related common misconception is that values of positive and negative feedbacks are assumed and directly programmed into the models. They are not. Positive and negative feedback are emergent properties that arise from interaction of multiple fundamental processes. Shock Brigade Harvester Boris (talk) 15:30, 30 December 2016 (UTC)

---

Re "What no one can dispute is already done damage like the rapidly dying glaciers everywhere in the world." and "just look at any glacier you like anywhere on our planet", no, not everywhere in the world. Most glaciers have been shrinking since the end of the little ice age (see Retreat of glaciers since 1850 and Glacier mass balance) but some are growing:

• NASA Study: Mass Gains of Antarctic Ice Sheet Greater than Losses
• "In 2002, scientists made the first detailed survey of Mount Shasta's glaciers in 50 years. They found that seven of the glaciers have grown over the period 1951-2002, with the Hotlum and Wintun Glaciers nearly doubling, the Bolam Glacier increasing by half, and the Whitney and Konwakiton Glaciers growing by a third." --Wintun Glacier
• "The Hubbard Glacier ice margin has continued to advance for about a century. " --Hubbard Glacier
• "Despite the volcanic activity, the glacier continued to advance and by mid-2008, the glacier completely encircled the lava domes. In addition, new glaciers (rock or ice) have formed around Crater Glacier as well." --Crater Glacier
• " Karakoram glaciers are mostly stagnating or enlarging" --Karakoram#Geology and glaciers
• "Measurements made at 9,200 feet (2,800 m) altitude show that glacier got 56 ft (17 m) thicker between 1994 and 1997, suggesting that it will probably begin advancing in the first decade of the 21st century." --Nisqually Glacier
• "Having retreated several kilometres between the 1940s and 1980s, the glacier entered an advancing phase in 1984 and at times has advanced at the phenomenal (by glacial standards) rate of 70 cm a day. The flow rate is about 10 times that of typical glaciers." --Franz Josef Glacier#Advance and retreat
• "The glacier is unusual in that it is advancing, while most glaciers worldwide are retreating." --Perito Moreno Glacier
• Glaciers in Norway Growing Again
• "Unlike most glaciers worldwide, it advanced significantly from 1945 to 1976 ... The glacier continued advancing both northward and southward in the fjord to near its present position" --Brüggen Glacier

This is not surprising, because the main drivers of glacial advancing/retreating are [A] how much it snows during the winter, and [B] whether summer is warm enough to melt the snow that fell the previous winter. You can have glacier growth during global warming if the warming mostly makes winters less cold. You can have glacier shrinkage during global cooling if the cooling leads to a dryer winter. --Guy Macon (talk) 16:01, 30 December 2016 (UTC)

• Both 1 and 2 have been proved "beyond a shadow of a doubt". Of course, there is always the slight possibility of scientists having been wrong - but just as much as for any other scientific topic, e.g. the mass of the electron might actually be much smaller or higher than what we think it is because of an unexplained effect that screwed up the measurements. However, while 1. has been quantified fairly accurately and (AFAIK) the mainsteam CC deniers have stopped contesting it, quantifying 2. is much harder. Plenty of unforeseen effects, feedback loops, etc. plus the usual difficulty in turning a measured correlation into a causal link.

Current CC deniers pound on that difficulty to quantify the effect to say (basically) that it is all a load of rubbish and should not be trusted. That is of course a logical fallacy. Imagine that in a room where the temperature is 20°C, a few people touch a radiator to evaluate its temperature and come up with widely different estimates (say two of them say 50°C and 90°C); it is hard to deduce the correct temperature of the radiator's surface (which is not surprising because humans are bad temperature detectors), but we can still deduce that the radiator is turned on. Tigraan^{Click here to contact me} 16:56, 31 December 2016 (UTC)

Why is the non dominant side of the body is stronger?

Why is the non dominant side of the body is stronger? For example, in a gym people can do more exercises repetitions (with dumbbell) with the non dominant hand. 93.126.88.30 (talk) 19:49, 29 December 2016 (UTC)

That may be your impression, but do you have any data that actually proves that it's true? I rather doubt that it is. In the literature of physical rehabilitation, it's often taken as a given that "the dominant hand possesses a 10% greater grip strength than the nondominant hand," exactly the opposite of your assumption. (This may be true only for right-handed people (see [10]) but nonetheless suggests that your impression isn't verified if you look at the data.) - Nunh-huh 20:09, 29 December 2016 (UTC)

Even within your question, you are intermixing two different ideas: strength and endurance. They may not even follow the same trend as each other, let alone your annecdotal report vs dominant hand, and one whole side might not be dominant either for different muscle groups. DMacks (talk) 21:09, 29 December 2016 (UTC)

It was written based on my feeling and my friend, we are both in the gym have the same thing: the dominant hand (right) is strong but the left has greater endurance (for me it's a result of strength). we can do more repetitions and even it's less heavier for me to take the weight in the non dominant hand. The same thing with my friend. Is it a random case or both of us indicate something that the most of the people have?93.126.88.30 (talk) 22:04, 29 December 2016 (UTC)

Could it be that you two are left handed and pulling people's legs here instead of weights?--TMCk (talk) 22:44, 29 December 2016 (UTC)

As I said we are totally right hand dominant (write in right, play in right, even the kicks are stronger in right, but when we are talking about lifting weights then left a little bit -but significantly- stronger.). No joking here. I'm absolutely serious. 93.126.88.30 (talk) 23:33, 29 December 2016 (UTC)

Just trying to rule out a (reasonable) possibility. --TMCk (talk) 23:40, 29 December 2016 (UTC)

It's also possible that any differences you are noticing in the gym are a result of what you're doing in the gym, rather than an inherent quality that is demonstrated in the gym. That is...something about the work-outs you've been doing for some time may have resulted in the differences you are seeing. In any case... more data is needed. - Nunh-huh 01:12, 30 December 2016 (UTC)

This could be connected with activities such as swinging a bat or chopping wood: The non-dominant arm is the "power" arm, and the dominant arm is the "control" arm. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:25, 30 December 2016 (UTC)

This is exactly what I assumed, but can you support it by scientific source? 93.126.88.30 (talk) 12:49, 30 December 2016 (UTC)

My source is something Ron Santo said a few decades ago when demonstrating how to hit a baseball. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:17, 30 December 2016 (UTC)

The terminology and techniques have changed over time, and "chopping wood" is now frowned upon (maybe that's why Ronnie struck out a lot). This is one viewpoint:[11] They're calling the right hand the power hand and the left hand the action hand. However, he's really saying the same thing Santo did, but with different words. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:39, 30 December 2016 (UTC)

Unlike baseball or tennis, where you whack the ball with the bat or racquet held horizontally, in the the sport of cricket the basic shots are played with the bat held vertically. And there is a school of thought that people who are right-hand dominant should bat "left-handed". David Warner, for example, pitches right-handed but bats left-handed.

(And while we're at it... Anecdote alert! There are a lot of fielding techniques cricket borrowed from baseball. I cycle past my alma mater's cricket oval - go shoppers - on my way home from work. There are often fielding drills on with the players wearing baseball gloves... and when a throw goes astray, they revert back and attempt to catch the ball with their glove-less dominant hand... )--Shirt58 (talk) 04:17, 1 January 2017 (UTC)

That's only for practice, where the players can't risk injuring their hands and fingers. The Law of Cricket #40 makes clear that the wicket keeper is the only player permitted to wear gloves in a game. Akld guy (talk) 20:56, 2 January 2017 (UTC)

The chemistry of baking bread

I tried baking my own bread before, and I failed. I thought I followed the recipe, but the results were as hard as a rock. I had well-portioned ingredients (flour, water, yeast, oil). I figured the salt and sugar were just for flavoring, so I dropped those things. I allowed the bread dough to rise and got the dough out to knead into a loaf of bread with extra flour and water. Then, I placed it into the oven to bake. Was I supposed to let it rise the second time? Or was I supposed to add the sugar for the yeast's consumption? Why do some bread recipes call for eggs, like challah? What's happening at the chemical level? 66.213.29.17 (talk) 20:49, 29 December 2016 (UTC)

I'm not sure about what exactly you did, but there are some important aspects. First, yes, sugar can give a boost the the yeast, and if used like that is usually added first (mix some flour, water, sugar and yeast, and let it rise a bit). Oil and salt are slowing the yeast down, so they should not be added to the starter, but only later. But do use salt - otherwise the bread will be very bland. Unless you use heavy processes and/or chemicals, you need to use wheat (or rye) flour, and you need to work the dough for a while to release enough gluten (in the case of wheat) to give the dough a good structure - about 15 minutes of kneading is recommended. Yes, before baking you need to let the bread rise again (which reminds me of Malcom Reynolds in Firefly - "we will rise again"). Chemically (or biologically), the yeast is converting sugar (and starch, which is just a complex sugar) into alcohols (which may contribute to the taste of the bread) and CO2, which let's the bread rise and gives the loaf its structure. You might want to take a look at yeast and Gluten#Bread_products. --Stephan Schulz (talk) 21:21, 29 December 2016 (UTC)

Another thing that can go wrong is the yeast. It could be dead to start with, although if you saw it rise it is probably live. When you let it rise the second time in the oven, do not make it too hot, else that will kill the yeast too. Graeme Bartlett (talk) 21:44, 29 December 2016 (UTC)

• I bake a lot of breads, but I guess this still OR. Good points made above already. Salt is indeed just for flavouring. Sugar is indeed theoretically there to kickstart the yeast, but I never use it and never have any problems with my rise. A lot of recipes do indeed call for the addition of oil, I've tried both with and without, and found the difference marginal, so don't use it. It does not significantly retard the rising. Salt can be added right at the start without any problems. You just have to be careful not to put it directly on the yeast. Even that's probably not too much of a problem when using modern dry yeast. So apart from being bland because of the lack of salt, there's likely nothing wrong with your recipe (assuming you used bread flour, rather than plain flour!)

It's after that where things went wrong, I'm afraid. Once you've kneaded your dough, you let it rise the first time. Chemically, the sugar that's released from the starches in the flour gets converted by the yeast into ethanol (which is by baking bread smells so nice!) and, crucially, CO₂, which is the gas that gives you the rise. You can't rush this. This is where people complain about the dough being 'retarded' if it rises slowly. This is a GOOD thing. The slower the rise, the more time the flavours have to develop. You can even proof overnight in the fridge. Unless you're in a hurry, a bit of retardation is nothing to be afraid of. Normally, this'll take a good hour or two for most flours.

At this point you 'knock back' the dough, that is compact it down again. Then you either shape it to the rough form you want, or put in in a tin, and let it rise again, for another hour or so at least. I would actually STRONGLY advise against doing this in even a low oven, as mentioned above, it'll rise it too quickly to get a flavourful bread. You do this for a number of reasons. As I said, the longer the rise, the better the flavour. However, you can't let a breast rise for hours and hours, as the bubbles will get too big and you'll have massive holes in your bread, or it will collapse. Also, by knocking it back, you make sure the bread is more homogeneous, you don't have pockets that are more or less risen. After that you bake it. Good tip to know when bread is done if you're not using a tin, tap the bottom. If it doesn't sound hollow, it's not ready.

As to why your bread is hard, there good be a number of reasons. It's probably a combination of a lack of gluten build up, and not enough rising, probably mostly the latter. Both are really bad for the texture of the bread. Dough almost always needs more kneading than you think (if doing it by hand). A good vigorous 10 minutes minimum. As far as rising, a second proof will probably sort that out. As for adding eggs or milk etc, this is called an enriched dough, which basically just means it's a bit more luxurious and special. It also alters the structure and colour of the bread. Hope that helps! Fgf10 (talk) 22:02, 29 December 2016 (UTC)

Watching "a breast rise for hours and hours" sounds like fun, to me. :-) StuRat (talk) 17:51, 30 December 2016 (UTC)

The secret to tasty bread is to start with flour, some water, and add a bit of yeast and put the whole thing in the fridge for 24-48 hrs to let flavour develop. If you don't do that, the bread will be tasteless. Then, take it out of the fridge and do as you wish. Options are as follows: You can knead it after the fridge a second time or not at all. You can not knead it before the fridge or not at all. Salt is good -- a lot of salt -- hard to oversalt it. No salt makes pretty tasteless bread. Add salt later or earlier. More time in the fridge means more taste and less need for salt. Before the fridge, make the dough loose, then add more flour, or not. Add milk for a fine crumb, if you like a fine crumb. Toss some whole barley or oat grains in there, or not, earlier or later, your pick. A dash of oil, no oil, a bit of sugar, a lot of sugar. All those things make different breads, but for sure, let the stuff rot in the fridge for a couple of days before you do anything with it. That is the secret. Trust me! I've made bread for many, many years. Anna Frodesiak (talk) 13:02, 30 December 2016 (UTC)

Oh, and you can oil a plastic bag and do most of this within the bag, including kneading. Saves a lot of hassle. I often never use a bowl, and so do others. Anna Frodesiak (talk) 13:06, 30 December 2016 (UTC)

@Anna Frodesiak: What a delightful insight you've given above. Guess I should retire my bread machine :) --TMCk (talk) 16:20, 30 December 2016 (UTC)

As some of the comments above. It may be the OP has chosen a grade of flour that produces a denser bread or that s/he hasn’t been knead enough to activate the gluten. Sure, there must be some youtube videos 'showing' how the texture changes when the dough has been kneaded enough to activate the gluten. For a beginner starting out, it may take more than 10 minutes of kneading until the technique becomes familiar. Then one doesn’t count the minutes but knead away (building up ones muscles) until the dough attains the right texture. Its repetition of action that leads to practice makes perfect. The Egyptians could have built pyramids out of my first early attempts.--Aspro (talk) 16:28, 30 December 2016 (UTC)

See 12 tips for perfect bread for some ideas of what can go wrong. Richerman (talk) 18:21, 30 December 2016 (UTC)